There has been known an electronic unit in which various electronic components are mounted on a substrate, the electronic components including a heating component that generates heat due to current supply, a temperature sensor that detects temperature, and a microcomputer. The microcomputer controls current supply such that temperature of the heating component is within an allowable temperature range, based on temperature detected by the temperature sensor and a value of integral of a current supplied to the heating component. In an electronic unit of JP2007-263636A, a notch groove is provided in a substrate portion around a temperature sensor mounted on the substrate to suppress transfer of heat generated by the heating component to the temperature sensor.
However, the substrate of the electronic unit of JP2007-263636A has the notch groove while still having a portion for an interconnection to be connected to the temperature sensor. Hence, if the interconnection connected to the temperature sensor continuously extends to a region in which a heating component is mounted, heat generated by the heating component may be directly transferred to the temperature sensor through the interconnection.
For the electronic unit of JP2007-263636A, the notch groove provided around the temperature sensor causes a large substrate size. Hence, when the electronic unit is reduced in size, the notch groove is apprehensively difficult to be provided in the substrate. Furthermore, for the electronic unit of JP2007-263636A, the notch groove provided around the temperature sensor degrades stiffness of the substrate. Hence, if the electronic unit is used in an environment that transmits oscillation and the like, the substrate may be cracked from the notch groove.